blowingagent

A blowing agent is a substance used to create a cellular or foamed structure in polymers and other materials by generating gas within the material during processing. The resulting gas forms bubbles that are trapped as the material cures or solidifies, producing a lightweight foam with properties such as low density, thermal insulation, and impact cushioning.

Blowing agents are commonly categorized as chemical blowing agents (CBAs) or physical blowing agents (PBAs). CBAs decompose or react to release gas, often nitrogen or carbon dioxide; well-known examples include azodicarbonamide and sodium bicarbonate–based systems. PBAs provide gas by vaporizing or expanding under processing conditions without chemical reaction; examples include low-boiling hydrocarbons such as pentane and cyclopentane, as well as compressed or supercritical carbon dioxide. Water can also act as a chemical blowing agent in polyurethane systems, reacting with isocyanates to generate CO2.

The choice of blowing agent influences cell structure, density, and properties of the foam. Open-cell foams have interconnected pores and typically lower density, while closed-cell foams trap gas more effectively, offering better insulation and moisture resistance. The size and uniformity of cells affect mechanical strength, thermal performance, and aging behavior.

Applications span a wide range of foamed products, including polyurethane and polystyrene insulation, automotive and consumer cushioning, packaging foams, and construction materials. Environmental and safety considerations are important: historical ozone-depleting blowing agents have been phased out or restricted, and many current agents have implications for global warming potential, flammability, or handling hazards. Selection balances performance, processing compatibility, cost, and regulatory requirements.